Research on microscale displacement characteristics of supercritical CO2 fracturing in shale oil reservoirs

The great success of CO₂ fracturing in shale oil reservoirs has not only increased the production capacity of shale oil, but also effectively carried out CO₂ geological storage. In this paper, focusing on the microscale displacement characteristics of CO₂ fracturing in shale oil reservoirs, first, the impact of oil saturation and gas invasion pressure on gas invasion is discussed. Then, the coupling control mode of oil saturation/pressure for various mechanisms of gas invasion is revealed. Results show that: (a) at lower displacement, the rock core has a lower initiation pressure and is fractured in a shorter period of time; (b) at higher displacement, the required fracturing time is longer and the fracturing pressure increases, but the fracturing effect is good and it is easy to form complex fracture networks; and (c) under higher pressure conditions, more complex fractures can be formed, which is beneficial for reservoir transformation and production improvement.